Diverse type underwater antennas responsive to electric and magnetic field components



Feb. '11, 1964 slLVERSTEIN 3,121,229

DIVERSE TYPE UNDERWATER ANTENNAS RESPONSIVE TO ELECTRIC AND MAGNETIC FIELD COMPONENTS Filed Jan. 31, 1961 FIGJ.

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ABRAHAM SILVERSTEIN ATTYS.

United States Patent DIVERSE TYPE UNDERWATER ANTENNAS RE- SPONSIVE TO ELECTRIC AND MAGNETIC FELD COMPONENTS Abraham Silverstein, 8609 14th Ave, Hyattsville, Md. Filed Jan. 31, 1961, Ser. No. 86,266 14 Claims. (Cl. 343-709) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to electromagnetic antennas and receiving systems and more particularly to such apparatus that is to be used under the water surface on submerged vehicles.

Previously, reception of very low frequency kilocycles to 100 kc. per sec.] electromagnetic energy under the water surface was accomplished by utilizing a pair of crossed loops, disposed at right angles to each other in a spherical watertight case.

In order for the spherical antenna to be useful to any great extent, it is necessary for it to be five or six feet in diameter. Such a large structure is disadvantageous because of the water drag and turbulence created when the submarine carrying the antenna moves through the water. This drag and turbulence has a tendency to impede submarine speed. The spherical construct-ion does not have great structural strength and is diificult to fabricate in a pressure resistant form. No portion of an underwater antenna can break the water level in order to properly receive electromagnetic energy. With a spherical antenna having a diameter of five to six feet, this requirement greatly restricts the maneuverability of the submarine carrying the receiving system.

Accordingly, it is an object of this invention to provide a new and improved omnidirectional antenna and receiving system especially adapted for underwater, very low frequency use.

Another object of this invention is to provide a new and improved underwater antenna which will not produce any drag on the submarine as it travels through the water and which will be mechanically sound.

A further object of this invention is to provide a new and improved underwater antenna that can easily be mounted on a submarine; which permits maximum submarine maneuvera-bility while continuously receiving electromagnetic energy; is easy and inexpensive to manufacture and install on a submarine; and has a high degree of reliability.

Various other objects and advantages will appear from the following description of several embodiments of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

The manner in which this invention achieves these objects can best be understood by reference to the accompanying drawing in which:

FIG. 1 is an illustration of a preferred form of the novel antenna constructed in accordance with this invention;-

FIG. 2 is an illustration of the antenna and its position on a submarine;

FIG. 3 is a schematic drawing of one form of the receiving apparatus utilized with this invention; and

FIG. 4 is a schematic drawing of another embodiment of the receiving apparatus utilized with this invention.

It is to be understood that like reference numerals designate like or similar parts through the several views.

Referring now to PEG. 1 of the drawings, which is an illustration of a preferred antenna structure 10 made in accordance with this invention, a longitudinal magnetic core 11, made from laminated iron or annealed iron wire, is completely surrounded by an electrical insulator. Coil 21 is wound around core 11 and produces across the terminals thereof a voltage indicative of the change in flux of the core.

The insulator comprises a hollow cylinder 12, preferably consisting essentially of fine, substantially rigid fiberglass fiber and a compliant, insulated filler 13 which may be either grease or oil. The filler 13 is employed to minimize damage to the antenna structure which results from pressure increases incurred when the antenna is lowered to great water depths. The core 11 is maintained in a fixed position by annular rings 14 and 15, made out of the same material as cylinder 12 and secured thereto. Also the ends of core 11 contact the respective ends of the glass fiber case 12, as shown on the drawing.

Secured to the ends of cylinder 12 are a pair of metallic electrodes 16' and 17, preferably made of silver and silver chloride or some other material that will not react with salt water. Wires 1% and 1%, soldered to electrodes 16 and 17, respectively, are partially embeded in the insulator and drawn through appropriate apertures in case 12. A voltage is produced across the wires 18 and 19 indicative of the electric field sensed by the electrodes 16 and 17.

When an electromagnetic signal is transmitted in the vicinity of the surface of the earth, a surface wave having a direction of signal propagation parallel to the surface of the earth is produced. The electric field vector associated with a surface wave is perpendicular to the surface of the earth and the magnetic field vector is perpendicular to both the direction of propagation and the the electric field vector, i.e. parallel to the ground. As the surface wave travels over a water medium, a certain amount of the energy is absorbed by the medium, causing an electromagnetic signal to be propagated through the water towards the center of the earth. As the signal propagates through the water in a vertical direction towards the bottom of the ocean, the magnetic field remains polarized in the same plane as it was in the surface wave but the electric field vector is rotated so that it is polarized in a plane parallel to the direction of propagation above the water. Thus, both the magnetic and electric field vectors are polarized parallel to the surface of the water when electromagnetic energy is being propagated through an aqueous medium.

When the coaxial antenna 1% of FIG. 1 is at a right angle to the propagation direction of very low frequency electromagnetic energy being transmitted through a water medium, the magnetic field produces a flux change in core 11 and the electric field produces a potential difference between electrodes 16 and 17. The fiux change in core 11 is in phase with the potential difference across electrodes 16 and 17. This flux change induces a voltage in coil 21 proportional to the core flux rate of change while the voltage generated between leads 18 and 19 is directly proportional to the potential difference between electrodes 16 and 17. Since the electromagnetic energy coupled to 3 the antenna is a very low frequency sinusoidal carrier, either pulse or amplitude modulated, the voltage induced in coil 21 will be substantially 90 out of phase compared to the voltage generated across leads l8 and 19.

It should be apparent that maximum voltages from both the magnetic and electric portions of the antenna are obtained when core ll is at right angles to the direc tion of electromagnetic wave propagation. Maximum reception of the electromagnetic energy will be obtained regardless of the antenna orientation in the plane at right angles to the direction of signal propagation. Thus, the antenna may be considered as omnidirectional if core 11 is maintained substantially perpendicular to the direction of electromagnetic propagation, i.e. parallel to the water surface.

This requirement is easily satifsfied if the length of cor ll of antenna It is mounted parallel to and in proximity to the submarine conning tower as illustrated on FIG. 2 of the drawings. With this arrangement, the longitudinal antenna axis, which is coincident with the core length, is maintained substantially parallel to the water surface for all tactical situations in which a submarine will be receiving electromagnetic signals. Thus, for any submarine orientation, maximum response will be obtained from the antenna mounted parallel to the longitudinal vehicle axis and the antenna may be considered omnidirectional. By placing this elongated, coaxial antenna on the conning tower, the entire antenna is able to come very close to the water surface and still maintain the entire submarine in a submerged position. This arrangement permits maximum signal reception because the antenna will not be surliciently submerged to cause great signal attenuation.

Referring now to FIG. 3 of the drawings, which illustrates one embodiment of the antenna and the associated receiving apparatus, comprising A.C. isolating amplifiers 31 and 32 connected to coil 21 and electrodes 16 and 17, respectively of antenna lit. The generated potential difference between electrodes 16 and 17 is coupled to amplifier 32. The outputs of amplifiers 31 and 32 are combined in a conventional adding circuit comprising isolating resistors 33 and 34, and summing amplifier 35. The voltage produced by amplifier 35 is a direct addition of the voltage between the electrodes and the voltage induced in coil 22. Thus, amplifiers 31, 32 and 35 and the circuitry associated therewith add the voltages generated across coil 21 and electrodes 16 and 17 so that the augend voltages, i.e. the inputs to amplifier 35, are maintained in the same relative phase relationship as existed in the generated voltages prior to amplification by amplifiers 31 and 32. The output of amplifier 35 is fed to a conventional very low frequency receiver 35 to provide an operator with an indication of the received energy.

If it is not important that the relative phase relationship between the signals be preserved or if it is necessary to have a wide frequency band receiver, the apparatus of FIG. 4 may be utilized. This embodiment is identical to that disclosed in FIG. 3 with the exception of detectors 3'7 and 38, which are respectively connected to the outputs of amplifiers 31 and The rectified DC. outputs of the detectors are combined in amplifier 35 and coupled to meter 39 or some other conventional indicator, such as a set of head phones.

If it is found desirable a small expansible bellows filled with oil or grease may be fitted over a vent in tie iibe glass case in order to prevent appreciable differential re sure on the case. it the oil is more compressible th water or if the oi has some entrapped air, the expansible bellows or an equivalent diaphram will flex as the ambient pressure is increased to equalize the internal and external pressures.

There has herein been disclosed a substantially omnidirectional, very low frequency electror gnetic antenna and receiving system which is mecha ind; and that does not impede the speed or manu.eurab....y oi the vessel upon which it is mounted.

It will be understood that various changes in the details, materials, and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An omnidirectional underwater antenna comprising an elongated magnetic core, an elongated, electrical insulator surrounding said core, a pair of electrodes, each of said electrodes being disposed solely at a respective end of said insulator, a pickup coil wound around a portion of said core for generating voltages in response to flux changes in said core, and a pair of electrical leads partially embedded in said insulator, each of said leads being separately connected to one of said electrodes, said leads generating voltages in response to potential difierence between said electrodes and means coupled to said coil and to said leads for combining the generated voltages.

2. The apparatus of claim 1 wherein said combining means includes means for adding the voltages generated in said core and said electrodes to maintain the same relative phase relationship in the added voltages as existed in the generated voltages.

3. The apparatus of claim 2 wherein said combining means includes a pair of isolation amplifiers and an adding circuit connected to said amplifiers.

4. The antenna of claim 1 wherein said insulator comprises a hollow cylindrical member comprising fine, glass fibers and a filler inserted between said cylindrical member and said core.

5. The antenna or" claim 1 wherein said core comprises a plurality of laminated iron strips.

6. The antenna of claim 1 wherein said core comprises an annealed iron wire.

7. Apparatus for receiving electromagnetic energy on an underwater vehicle comprising an antenna having an elongated magnetic core, an elongated electrical inslator fixed to and surrounding said core, a pair of electrodes, each of said electrodes being disposed solely at a respective end of said insulator, said core being mounted on the exterior of the vehicle in a plane parallel to the deck of the vehicle, and means coupled to said core and said electrodes for combining the voltages generated in said core and said electrodes.

8. The apparatus of claim 7 wherein said combining means includes means to add the voltages and to maintain the same relative phase relationship in the added voltages as existed in the generated voltages.

9. The apparatus of claim 7 wherein said combining means includes a pair of detectors, one of said detectors being coupled to said core and one of said detectors being coupled to said electrodes, and means coupled to both of said detectors for adding the outputs thereof.

10. Apparatus for receiving electromagnetic energy on an underwater vehicle comprising an antenna having an elongated magnetic core containing a plurality of laminated iron strips, an elongated electrical insulator having a hollow, cylindrical, glass fiber member and a grease filler inserted in the member, said insulator fixed to and surrounding said core, a coil wound on said core, a pair of electrodes, each of said electrodes being disposed solely at a respective end of said insulator, said core being mounted on the exterior of the vehicle in a plane parallel to the longitudinal axis of said vehicle, and means coupled to said coil and said electrodes for adding the voltages generated across said coil and said electrodes and to maintain the same relative phase relationship in the added voltages as existed in the generated voltages.

ll. Apparatus for detecting a low frequency electromagnetic wave signal being propagated in a water medium having a magnetic component and an electrical component comprising a magnetic core means for detecting the magnetic component, electrode means for detecting the electrical component, insulating means providing a direct magnetic path between the water medium and said magnetic core means for making a waterproof closure about said magnetic core means and for electrically insulating said electrode means from said magnetic core means, and circuit means coupled to both said magnetic core means and said electrode means vfor adding the outputs thereof.

12. The apparatus of claim 11 wherein said magnetic core means comprises a straight elongated magnetic core.

13. The apparatus of claim 12 wherein said electrode means comprises a pair of electrodes disposed on a line substantially parallel to the elongated axis of said magnetic core.

14. The apparatus of claim 13 wherein said electrodes References Cited in the file of this patent UNITED STATES PATENTS 2,581,348 Bailey Jan. 8, 1952 FOREIGN PATENTS 217,245 Great Britain Dec. 7, 1925 480,853 Germany Aug. 9, 1929 680,280 Great Britain Oct. 1, 1952 

1. AN OMNIDIRECTIONAL UNDERWATER ANTENNA COMPRISING AN ELONGATED MAGNETIC CORE, AN ELONGATED, ELECTRICAL INSULATOR SURROUNDING SAID CORE, A PAIR OF ELECTRODES, EACH OF SAID ELECTRODES BEING DISPOSED SOLELY AT A RESPECTIVE END OF SAID INSULATOR, A PICKUP COIL WOUND AROUND A PORTION OF SAID CORE FOR GENERATING VOLTAGES IN RESPONSE TO FLUX CHANGES IN SAID CORE, AND A PAIR OF ELECTRICAL LEADS PARTIALLY EMBEDDED IN SAID INSULATOR, EACH OF SAID LEADS BEING SEPARATELY CONNECTED TO ONE OF SAID ELECTRODES, SAID LEADS GENERATING VOLTAGES IN RESPONSE TO POTENTIAL DIFFERENCE BETWEEN SAID ELECTRODES AND MEANS COUPLED TO SAID COIL AND TO SAID LEADS FOR COMBINING THE GENERATED VOLTAGES. 